The present invention relates to traveling grates of the type used to convey material through a dryer, a furnace or a discharge zone to a rotary kiln. More particularly, the present invention relates to a side plate construction for a traveling grate that increases the life of the side plate by reducing the temperature gradients across the side plate.
It is conventional in the prior art to provide vertically extending side plates which travel with a traveling grate or grate conveyor to retain the material being conveyed, such as pelletized ore or the like, on the traveling grate. A plurality of such side plates are pivotally connected in overlapped relation to each other along each of the lateral sides of the conveyor. Such overlapped side plates are conventionally positioned laterally on outer ends of the respective through rods or tie rods of the grate conveyor.
In the construction of the prior art, the overlapped side plates of the traveling grate chain assembly experience severe cracking that requires changing side plates after 1xc2xd to 2 years of operation. The severe cracking of the side plates is believed to be caused by several contributing factors. Severe thermal cycling from the inlet of the traveling grate to the discharge end of the grate is an obvious effect of the process that cannot be changed and will probably worsen as the capacity of the traveling grate increases. Large thermal gradients across the side plates are evident from infrared pictures, and the effect is to put a severe strain on the side plates from the differences in the thermal expansion in different areas of the side plate. Stress risers from small radii in the corners of the side plates are inherent in the casting process. Three factors that are not readily obvious but contribute to the cracking problems in conventional side plates are: the restraining effects of the existing gussets, the cooling effects of the existing gussets, and the heat concentration in the back portion of the side plate due to overlapping of the back portion by the front portion of the preceding plate.
Therefore, it is an object of the present invention to provide an improved side plate that promotes heat transfer away from the side plate to reduce temperature gradients across the side plate resulting in reduced thermal stress in the side plate. Further, it is an object of the present invention to provide a side plate that is devoid of any gussets, which allows the side plate a greater degree of expansion and reduces the cooling effect created by the gussets. Further, it is an object of the present invention to provide a side plate that extends the effective life of the side plate and reduces the tendency of the side plate to crack due to the temperature gradients developed over the side plate.
The present invention is a side plate for use with a traveling grate. The side plate of the present invention decreases the thermal gradients across the front portion of the side plate while allowing heat to be radiated from the overlapped, back portion of the side plate when the side plate is positioned adjacent to a leading side plate.
The side plate of the present invention includes a heat transfer opening formed in the front portion of the side plate. The heat transfer opening is a removed area of the front portion of the side plate and provides an opening through the front portion of the side plate. The heat transfer opening formed in the front portion of the side plate overlays the back portion of the immediately trailing side plate when the side plates are sequentially connected to the continuous length of conveyor chain. The heat transfer opening allows heat to be radiated from the overlapped area of the back portion of the side plate, such that the overlapped area of the back portion can radiate heat effectively to reduce the temperature gradient across the back portion of the side plate to reduce thermal stress in the side plate.
The side plate of the present invention includes a front portion that has the gussets removed such that the entire front portion is generally planar. The removal of the gussets from the front portion of the side plate eliminates the increased heat transfer that previously occurred due to the gussets extending from the front portion. Additionally, the removal of the gussets allows the entire front portion of the front plate to expand and contract at a constant rate.
These two advantages decrease the temperature gradients across the side plate, thereby decreasing the cracking of the side plate and extending the useful life of the side plate.